1. Field of the Invention
The present invention relates to a method for manufacturing an ink jet recording head that records by discharging recording liquid onto a recording sheet. The invention also relates to an ink jet recording head manufacturing by such method of manufacture, and an ink jet recording apparatus having such ink jet recording head mounted thereon. More particularly, the invention relates to a method for manufacturing an ink jet recording head, which provides an improved method for coating filling agent on the circumference of the recording elemental substrates that constitute the ink jet recording head. The invention also relates to an ink jet recording head manufactured by such method of manufacture, as well as to an ink jet recording apparatus having such ink jet recording head mounted thereon.
2. Related Background Art
Generally, an ink jet recording apparatus is a recording apparatus that records by discharging recording liquid from the discharge ports onto a recording sheet. The apparatus comprises the ink jet recording head that forms recording liquid droplets which are discharged from the discharge ports, and the supply system that supplies recording liquid to the ink jet recording head.
The aforesaid ink jet recording apparatus is a recording apparatus of the so-called non-impact recording type, which makes it possible to perform a high speed recording on various recording media. The apparatus is also characterized in that it has almost no noises at the time of recording. Therefore, the apparatus is widely adopted as an apparatus that carries the recording mechanism, such as a printer, a word processor, a facsimile equipment, and a copying machine, among some others.
As the typical recording method that adopts the ink jet recording apparatus, there is the one that uses electrothermal converting elements. This method uses electrothermal converting elements for the pressure chamber which is arranged in the vicinity of the discharge ports. With the application of electric pulses that become recording signals provided for such elements to discharge the recording liquid from fine discharge ports as liquid droplets by the utilization of pressure exerted by bubbling (film boiling) of the recording liquid, hence performing the recording on the recording sheet.
Here, for the aforesaid discharge method of recording liquid, there is the type where the recording liquid is discharged in the direction parallel to the substrate having the electrothermal converting elements arranged thereon (that is, an edge shooter). Also, there is the one where the recording liquid is discharged in the direction perpendicular to the substrate where the electrothermal converting elements are arranged thereon (that is, a side shooter).
FIG. 1 is a view which shows the general recording elemental substrate. FIG. 2 is a view which shows the state where the recording elemental substrate represented in FIG. 1 is connected with a wiring substrate.
As shown in FIG. 1 and FIG. 2, a plurality of discharge ports 2 are arranged on one side face of the recording elemental substrate 1 with recording elements for discharging recording liquid provided therefor. On the other face, the supply port 3 is arranged open in order to supply the recording liquid to the discharge ports 2 in a length almost equal to the length of the discharge port array 2. Then, the wiring substrate 4 is connected with the recording elemental substrate 1 by the application of the TAB assembling techniques or the like in order to apply the electric pulses for discharging the recording liquid. In this way, the recording element unit 6 is formed. Here, the wiring of the wiring substrate 4 is arranged on the reverse side thereof (not shown).
Also, on the recording elemental substrate 1, the sealing resin 5 is coated to protect the lead lines (not shown) that electrically connect the recording elemental substrate 1 and the wiring substrate 4 from erosion by the recording liquid, as well as from the breakage due to the force that may act from the outside.
FIG. 3 is an exploded perspective view which shows one structural example of the conventional ink jet recording head having the recording element unit 6 illustrated in FIG. 2 is arranged therefor. FIG. 4 is a perspective view which shows the external appearance after the completion of the assembling of the ink jet recording head illustrated in FIG. 3. FIG. 5 is a partially enlarged view of the section taken along line V—V in FIG. 4.
As shown in FIG. 3 and FIG. 4, a plurality of the recording element units 6a to 6c are adhesively fixed to the upper face of the supporting member 7 through the supporting plates 8a to 8c (also referred to below as supporting plate 8) by the application of the bonding resin 9a to 9c, the bonding resin 10a to 10c, and the bonding resin 11a to 11c. Also, on the side face of the supporting member 7, the wiring integration substrate 12 is fixed in order to put electric signals together for a plurality of wiring substrates 4a to 4c, and then, electrically connected with a plurality of the wiring substrate 4a to 4c. In this respect, a reference numeral 20 designates the ink supply port.
Thus, as shown in FIG. 4, the face of the ink jet recording head on the recording liquid discharge port side is filled with the sealing resin 13a on the supporting plate 8, the opening portion of the recording element unit 6, and the circumference of the wiring substrate 4 (so as not to allow the supporting plate 8 to be exposed), hence protecting the wiring on the reverse side of the wiring substrate 4 from the recording liquid.
Also, in addition to the function that supports and fixes the wiring substrate 4, the supporting plate 8 functions as the heat radiation member that radiates heat generated by the recording elemental substrate 1. For this plate, therefore, it is generally practiced to use aluminum or some other material having good heat radiation. Consequently, as in the case of the wiring substrate 4, the supporting plate 8 should also be protected from the recording liquid by filling the sealing resin 13b on the circumference thereof.
However, the circumference of the recording elemental substrate 1 and the circumference of the wiring substrate 4 of the conventional ink jet recording head are sealed as described above in order to execute the sealing process efficiently in a short period of time, with the sealing resin 13a and 13b (also referred to below as sealing resin 13), as shown in FIG. 5.
As a result, there is a need for securing an area between the recording elemental substrate 1 and the wiring substrate 4 at least in the size which may allow the needle of the sealing resin coating machine to enter between them. The outer dimension of the wiring substrate 4 should then become larger by that portion inevitably.
Also, since the electric wiring pattern on the recording elemental substrate 1 is assembled by the application of the photolithographic techniques in high density up to the circumferential portion of the surface thereof, there is a possibility that even a small chipping on the outer circumference may cause the defective performance. Therefore, in order to protect the exposed portion of the electric wiring of the recording element unit, filler is filled in the circumference thereof. Then, it is necessary to execute this filling in good precision so that the coating machine is not allowed to touch the recording elemental substrate.
Also, the sealing resin 13 is directly coated on the circumference of the recording elemental substrate 1, which makes it necessary to control the coating amount exactly. If the coating amount is too large, the sealing resin 13 may be caused to spread out to the surface of the recording elemental substrate 1 or the wiring substrate 4. If the recording head is completed in such a state that the sealing resin spreads out, it may become an obstacle when the surface of the recording elemental substrate 1 is cleaned after printing.
Also, depending on the viscosity of the sealing resin 13 and the thixotropy thereof, a cobwebbing phenomenon may take place when the needle of the coating machine leaves the sealing portion. In some cases, the sealing resin 13 adheres to the surface of the recording elemental substrate 1 in stripes, which may also become an obstacle when the cleaning is made as described above.
Also, when both sides of the recording elemental substrate 1 are sealed almost simultaneously, the air should remain to reside inevitably on the reverse side of the connecting portion (that is, the portion where the sealing resin 5 is applied) between the recording elemental substrate 1 and the wiring substrate 4. The bubbles of the air thus residing tend to escape externally by breaking the layer of the sealing resin 13 or to stay on the inner side. If they escape externally, holes are formed in the layer of the sealing resin 13, which results in sealing defects. Further, if the bubbles are broken, the surface of the recording elemental substrate 1 may be stained by the adhesion of the sealing resin 13.
Also, if the bubbles remain on the inner side, the reverse side of the connecting portion (that is, the portion where the sealing resin 5 is applied) between the recording elemental substrate 1 and the wiring substrate 4 becomes hollow. Thus, there is a possibility that the wiring of the wiring substrate 4 is eroded by the recording liquid that may enter the reverse side of the wiring substrate 4 from such portion that may become hollow.
Therefore, it is ideal to adopt a coating method which does not allow any bubbles to remain on the reverse side of the connecting portion (that is, the portion where the sealing resin 5 is applied) between the recording elemental substrate 1 and the wiring substrate 4. Then, if the sealing resin 13 is coated directly on the circumference of the recording elemental substrate 1, it is necessary to control the timing, the amount, and the coating frequency when one side of the sealing portions of the recording elemental substrate 1 is coated and the other side thereof is coated as the case may be.
However, if the coating timing, amount, and frequency should be controlled appropriately as described above, there is a fear that the time required for the sealing process is inevitably increased to a considerable extent.
Conventionally, therefore, there is still a room for improvement as to the satisfactory control of the appropriate filling amount in order to execute the filling of the filler in good precision when the filler is filled on the circumference of the recording elemental substrates as has been discussed above.